1. Field of the Invention
The present invention relates to wound dressing materials comprising complexes formed between anionic polysaccharides, such as oxidized regenerated cellulose (ORC), and silver, and to the uses thereof for the treatment of wounds.
2. Background of the Invention
Anionic polysaccharides such as alginates, hyaluronic acid and its salts, and oxidized celluloses such as oxidized regenerated cellulose (ORC) are known for use as wound dressing materials. Alginates and ORC are hemostatic when applied to a wound.
EP-A-0437095 describes the preparation of a neutralized ORC fabric by reacting ORC with a buffered solution of a salt of a weak acid, such as sodium acetate. The use of a buffered reagent is said to result in less breakdown of ORC fabrics. The neutralized ORC can support further acid-sensitive hemostatic agents such as thrombin or t-PA.
WO98/00180 describes the use of freeze-dried sponges of collagen admixed with oxidized regenerated cellulose (ORC) for the treatment of chronic wounds. The mixed sponges provide enhanced healing of chronic wounds such as venous ulcers, decubitis ulcers and diabetic ulcers. The specification mentions that silver sulfadiazine or chlorhexidine may be present as an antiseptic additive.
GB-A-748283 describes complexes of polysaccharides with various metals, including silver. WO91/11206 describes the use of silver alginate salts in wound dressings. WO87/05517 describes silver salts of hyaluronic acid that may be used as or in antimicrobial wound dressings.
WO02/43743 describes wound dressings comprising a silver salt of an anionic polysaccharide, and further comprising a substance to improve the photostability of the silver salt. The stabilising substance may include ammonia, ammonium salts, thiosulphates, chlorides and/or peroxides. In one preferred embodiment, the stabilising agent is aqueous ammonium chloride.